Modern Views on the Composition of Anionic Oxy-Fluoride Complexes of Aluminium and Their Rearrangement during the Electrolysis of Cryolite-Alumina Melts

摘要

Some consequences of the hypothesis of the absence of free F~- ions in cryolite-alumina melts are observed. The melt at 1 < CR < 3 is assumed to consist of the complexes AlF_6~(3-) , AlF_5~(2-), AlF_4~- , Al_2OF_6~(2-) and Al_2O_2F_4~(2-) , and alkali metal cations. A formal-stoichiometric study of the processes occurring during electrolysis is performed on the basis of the accepted hypothesis. Judgments about some of the features of the electrode reactions and chemical reactions in the electrolyte volume are presented. The reaction schemes for the instances with and without the subsequent/preceding chemical reaction near the electrode or in the molten salt volume are given. The mass flows of various forms of ionic complexes through the electrolyte volume are given for these schemes. Definitive conclusions are not made in the study, but the range of possible variants for the electrochemical routes of the overall chemical reaction in the cell is limited.